The metallic model: notes and practice questions
- This topic explains the metallic model of bonding and how it accounts for the characteristic properties of metals.
- A metallic bond is the electrostatic attraction between a lattice of positive metal ions and delocalized electrons.
- Delocalized electrons enable metals to conduct electricity and heat.
- The non-directional nature of metallic bonding allows metal ions to slide past each other, explaining malleability.
- The strength of a metallic bond increases with higher charge of the metal ions and smaller ionic radius.
- Trends in melting points of s-block and p-block metals can be explained by the strength of their metallic bonds.
How it is examined
Short. Usually one Paper 1A item on why metals conduct or why Mg melts higher than Na, and occasionally a 2-mark Paper 2 explanation. The malleability explanation wants layers of cations sliding while the delocalized electrons keep the attraction intact; "the atoms can move" does not earn it.
Ionic radii and melting points. The model itself is recall.
- 2.3.1 A metallic bond is the electrostatic attraction between a lattice of cations and delocalized electrons. Students explain the electrical conductivity, thermal conductivity and malleability of metals.
- 2.3.2 The strength of a metallic bond depends on the charge of the ions and the radius of the metal ion. Students explain trends in melting points of s and p block metals.
2.3.3 Transition elements have delocalized d-electrons. Students explain the high melting point and electrical conductivity of transition elements.
Guiding questions
- What determines the metallic nature and properties of an element?
Linking questions
- Tool 1, Inquiry 2, Structure 3.1 What experimental data demonstrate the physical properties of metals, and trends in these properties, in the periodic table?
- Reactivity 3.2 What trends in reactivity of metals can be predicted from the periodic table?
- Structure 2.4 What are the features of metallic bonding that make it possible for metals to form alloys?
- Structure 3.1 (HL) Why is the trend in melting points of metals across a period less evident across the d-block?
Practice questions
19 questions · 11 easy · 8 mediumQuestion 1
EasyPaper 1A · calculator1 markAn unknown silvery solid is analysed and found to have the following properties:
• High melting point ( °C)
• Excellent electrical conductor as a solid
• Excellent electrical conductor when molten
• Malleable and ductile
What is the most probable structure of this substance?
A. Ionic lattice
B. Metallic lattice
C. Simple molecular
D. Covalent network
Consider how the mobility of charged particles (electrons or ions) in the solid and molten states affects electrical conductivity for each bonding type. Also, think about how the layers of particles can move relative to each other in each structure.
Question 2
MediumPaper 1A · calculator1 markWhich sequence correctly lists the elements in order of decreasing melting point?
A.
B.
C.
D.
Melting point is a measure of the strength of the metallic bond. Consider how the number of delocalized valence electrons and the nuclear charge change across a period.
Question 3
EasyPaper 1A · calculator1 markWhich statement best explains the high electrical conductivity of aluminium?
A. The strong electrostatic attraction between aluminium ions and delocalized electrons holds the lattice firmly.
B. The delocalized valence electrons are mobile and can move throughout the metallic structure.
C. The layers of aluminium ions can slide over one another without disrupting the metallic bond.
D. Aluminium atoms are closely packed in a crystal lattice structure.
Consider what is necessary for a substance to conduct electricity. Which particles in a metal are free to move and can therefore carry an electrical charge?
Question 4
MediumPaper 2 · calculator5 marksBrass is an alloy of copper and zinc.
(a) Describe the bonding in brass.
(b) Suggest why brass conducts electricity but zinc sulfide, an ionic compound, does not conduct electricity in the solid state.
An alloy is a mixture of metals. What type of bonding is present in metals? Describe the particles involved and the forces between them.
Electrical conductivity requires mobile charged particles. Compare the particles present in brass and solid zinc sulfide and their ability to move.
Question 5
EasyPaper 2 · calculator4 marksA key property of metals is their ability to conduct electricity.
(a) Describe the structure and bonding in metals.
(b) Explain, with reference to your answer in (a), why metals are good electrical conductors.
Consider the arrangement of atoms in a solid metal and the nature of their valence electrons. What holds the structure together?
Relate the movement of charged particles to the flow of electricity. Which particles in the metallic structure are mobile?
Question 6
MediumPaper 2 · calculator3 marksElectrical conductivity is a characteristic property of metals. Identify which of the Period 3 metals, sodium, magnesium, or aluminium, is the best electrical conductor. Explain your reasoning in terms of their metallic structure and bonding.
Consider the number of delocalized electrons each metal atom contributes to the 'sea' of electrons. How does this relate to the ability to carry an electric current?
Question 7
EasyPaper 2 · calculator2 marksPure gold, also known as 24-carat gold, is a relatively soft metal. For use in jewelry, it is often alloyed with other metals like copper to produce 18-carat gold.
(a) Explain, with reference to their structures, why 18-carat gold is harder than 24-carat gold.
Consider the arrangement of atoms in a pure metal compared to an alloy. How does the presence of atoms of different sizes affect the way layers of atoms can move past each other?
Question 8
MediumPaper 2 · calculator3 marksHigh-voltage power lines are typically made of aluminium rather than copper, despite copper having a higher electrical conductivity. Explain, with reference to two distinct physical properties, why aluminium is often the preferred material for this application.
Consider the practical challenges of suspending long, heavy cables between pylons over large distances. What properties, besides conductivity, would be important for the material used?
Question 9
EasyPaper 1A · calculator1 markA white crystalline solid is investigated. It is found to be brittle, has a high melting point, and does not conduct electricity in the solid state. However, it conducts electricity when dissolved in water. Which type of bonding best describes this solid?
A. Covalent molecular
B. Covalent network
C. Ionic
D. Metallic
Consider the state in which the substance conducts electricity. What does this tell you about the charge carriers (electrons or ions) and their mobility in different states?
Question 10
MediumPaper 1A · calculator1 markBrass is an alloy of copper and zinc. Like pure copper, it is ductile, meaning it can be drawn into a wire. What is the best explanation for the ductility of brass?
A. The zinc atoms are smaller than copper atoms, allowing layers to slip.
B. The electrostatic attraction between the sea of delocalized electrons and the metal cations is maintained as the layers of atoms move.
C. The covalent bonds between copper and zinc atoms are flexible.
D. The alloy has a low melting point, which makes it easy to deform.
Consider the fundamental model of metallic bonding. How does this model account for properties like ductility and malleability? Remember that alloys are mixtures of metals and still exhibit metallic bonding.
Question 11
EasyPaper 1A · calculator1 markWhich element is expected to have the highest melting point?
A. Li
B. Na
C. K
D. Rb
Melting point is related to the strength of the forces between particles. In metals, this is the metallic bond. Consider how the strength of the metallic bond changes down Group 1.
Question 12
MediumPaper 1A · calculator1 markThe strength of the metallic bond influences physical properties such as melting point. Which metal is expected to have the highest melting point?
A. Na
B. K
C. Li
D. Mg
Consider the factors that determine the strength of a metallic bond: the number of delocalized valence electrons and the radius of the metal cation. Compare the elements based on their positions in the periodic table.
Question 13
EasyPaper 1A · calculator1 markAn unknown substance is a lustrous solid at room temperature. It is found to have a high melting point and is an excellent electrical conductor in its solid form. Which structure best describes this substance?
A. Ionic lattice
B. Metallic lattice
C. Simple molecular
D. Covalent network
Consider the properties of each type of structure. Which one contains mobile charged particles in the solid state that would allow for electrical conductivity?
Question 14
MediumPaper 1A · calculator1 markThe structure of a solid metal is often described as a lattice of positive ions surrounded by a 'sea' of delocalized electrons. Which statement is a correct consequence of this model?
A. Metals are brittle as strong repulsive forces are created when layers of ions are displaced.
B. Metals conduct electricity in the solid state because the positive ions are mobile and carry charge.
C. Metals are malleable because the metallic bond is non-directional, allowing layers of ions to slide over one another.
D. Metals have low electrical conductivity because the delocalized electrons are strongly held by individual ions.
Consider the key features of the metallic bonding model: what are the particles involved, are they mobile or fixed, and what is the nature of the attraction between them? How does this explain the ability of metals to be shaped without breaking?
Question 15
EasyPaper 1A · calculator1 markA white crystalline solid is found to have a high melting point. It does not conduct electricity in the solid state, but it does conduct electricity when molten. Which type of structure and bonding is present in the solid?
A. Metallic
B. Ionic
C. Covalent molecular
D. Covalent network
Consider what particles are responsible for electrical conductivity. In which types of substances are these particles mobile in the solid state, and in which are they only mobile when the substance is molten or dissolved?
Question 16
MediumPaper 1A · calculator1 markThe properties of four substances, each formed from two different elements, are listed. Which substance is most likely to be ionic?
| Option | Average electronegativity | Electronegativity difference |
|---|---|---|
| A | 1.5 | 0.4 |
| B | 3.0 | 0.1 |
| C | 2.1 | 2.8 |
| D | 2.8 | 1.2 |
A. Average electronegativity = 1.5; Electronegativity difference = 0.4
B. Average electronegativity = 3.0; Electronegativity difference = 0.1
C. Average electronegativity = 2.1; Electronegativity difference = 2.8
D. Average electronegativity = 2.8; Electronegativity difference = 1.2
Consider the definition of an ionic bond in terms of electronegativity. What kind of elements form ionic bonds, and what does this imply about their individual electronegativity values and the difference between them?
Question 17
EasyPaper 1A · calculator1 markWhich statement best explains why solid aluminium is a good electrical conductor?
A. The layers of positive aluminium ions can slide over one another.
B. The delocalized valence electrons are mobile and can move through the lattice.
C. There are strong electrostatic forces of attraction between the aluminium ions and the delocalized electrons.
D. Aluminium atoms are closely packed in a crystal lattice structure.
Electrical conductivity involves the movement of charged particles. What particles are free to move in a metallic structure?
Question 18
EasyPaper 1A · calculator1 markWhich metal is expected to have the highest melting point?
A. Na
B. Mg
C. Ca
D. Al
The melting point of a metal is related to the strength of its metallic bonding. Consider the number of delocalized valence electrons and the charge of the resulting metal cation for each element.
Question 19
EasyPaper 1A · calculator1 markWhich statement best explains why metals are good electrical conductors?
A. The metal cations are mobile and can move through the lattice.
B. The delocalized electrons are mobile and can act as charge carriers.
C. The electrostatic attractions between cations and electrons are very strong.
D. The metal atoms are arranged in a regular, closely packed lattice.
Consider the structure of a metal. What particles are present, and which of them are free to move to carry an electrical current from one end of the metal to the other?
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Where marks are lost
- Reaching for "human error" or "only one trial." A source of error has to be a specific step in the method, not a general apology for the result.
- Joining the dots instead of drawing a curve.
- Naming a chemical instead of the property that distinguishes it, or vice versa. Answering with the nearest fact that comes to mind rather than the fact the command term and stem jointly ask for is a recurring way to answer a question that was not, quite, the one asked.
